Physics - Online Test
Q1. The number of significant digits in 0.2370 is
Answer : Option C
Explaination / Solution:
There are three rules on determining how many significant figures are in a number:
- Non-zero digits are always significant.
- Any zeros between two significant digits are significant.
- A final zero or trailing zeros in the decimal portion ONLY are significant.
So keeping these rules in mind, there are 4 significant digit.
Q2. An inductor with L = 9.50 mH is connected across an ac source that has voltage amplitude 45.0 V. Frequency of the source that results in a current amplitude of 3.90 A is
Answer : Option B
Explaination / Solution:
Frequency of the source
Q3. A potentiometer has a uniform wire of length 10m and resistance 5 ohms. The potentiometer is connected to an external battery of emf of 10V and negligible internal resistance and a resistance of 995 ohms in series. The potential gradient along the wire is:
Answer : Option D
Explaination / Solution:
The total resistance is the sum of the resistance of the potentiometer and the external resistance.
R = Rpot + Rext = 5 + 995 = 1000 ohms .
The current through the potentiometer wire I = E/R = 10/1000 = 0.01A.
The potential drop across the potentiometer wire is
The potential gradient = ( potential drop across the potentiometer wire)/ length of the potentiometer wire)
= 0.05/10
= 5 × 10-3 V/m
= 5 m V/m
Q4. A pendulum suspended from a ceiling of a train has a period T when the train is at rest. When the train is accelerating with a uniform acceleration α, the period of oscillation will
Answer : Option B
Explaination / Solution:
No Explaination.
Q5. A magnet of magnetic moment is aligned in the direction of magnetic field of 0.1.T. What is the net work done to bring the magnet normal to the magnetic field?
Answer : Option B
Explaination / Solution:
The potential energy of a magnetic dipole of moment m placed in a magnetic field is .When the magnet is aligned in the direction of the field, and the initial potential energy When the magnet is placed perpendicular to the direction of the field,its potential energy is .Work done in rotating the magnet is equal to the change in its potential energy.
Q6.
Assume that light of wavelength 6000 is coming from a star. What is the limit of resolution of a telescope whose objective has a diameter of 100 inch?
Answer : Option C
Explaination / Solution:
No Explaination.
Q7. An iron bar magnet of length 10cm and cross section 1 has a magnetization of . Magnet's pole strength is
Answer : Option A
Explaination / Solution:
No Explaination.
Q8. P-N junction can be used as
Answer : Option A
Explaination / Solution:
The resistance of p-n junction diode becomes low when forward biased and becomes high when reverse biased. Therefore it allows the current to pass through it when it is forward biased and does not allow when reverse biased. Hence it can rectify AC into DC.
Q9. Motion along a straight line is called __________.
Answer : Option A
Explaination / Solution:
Rectilinear motion is another name for straight-line motion. This type of motion describes the movement of a particle or a body. A body is said to experience rectilinear motion if any two particles of the body travel the same distance along two parallel straight lines.
Q10. The fundamental frequency of an open pipe is N keeping the pipe vertical. It is submerged in water so that half of its length is filled with water. The fundamental frequency of air column is
Answer : Option A
Explaination / Solution:
No Explaination.
